Complicated electronic systems are often constructed using multiple sub-assemblies. Often, electronic circuits are built on printed circuit boards. Each printed circuit board might contain circuitry that performs a specific function. For example, one circuit board in an electronic system might contain a processor and supporting circuitry while another circuit board might contain memory. Providing subassemblies that contain specific functions allows significant flexibility in assembling or servicing an electronic system because the circuitry for a specific function can be removed, added or replaced.
Often, electrical connections between the circuit boards are made through a backplane. An electrical backplane is a printed circuit board predominantly containing traces that carry electronic signals. The circuit boards implementing specific functions are often called “daughter cards.” Connectors are mounted on the backplane and make electrical connection to the traces. Complimentary connectors are mounted on the daughter cards.
The backplane is often mounted in a card cage or other support structure. To assemble a system, daughter cards are inserted into the card cage such that the electrical connectors on the daughter cards mate with the electrical connectors on the backplane. In operation, electrical signals pass from one daughter card to another through the backplane.
As electronic systems have become more sophisticated, there has been a need to pass more data between daughter cards. To handle higher data rates, some electronic systems employ light signals to transmit data. The light is routed from circuit component to circuit component using optical wave guides. The optical wave guides are often in the form of fiber.
When optical fiber is used to route signals within an electronic assembly, it is desirable to maintain the modular architecture of the electronic system. It would, for example, be desirable to manufacture the system as separate modules resembling conventional printed circuit boards. To retain that architecture with optical connections, blind mate optical connectors are required.
Blind mate connectors are constructed to mate when pressed together. They can mate without the need for physical access to the connector. Blind mate connectors are particularly well suited for use in a daughter card/backplane configuration because the backplane is generally not easily accessible from the outside of the card cage housing the electronic system. Inserting a daughter card into the card cage provides the force needed to mate the blind mate connectors. Blind mate electrical connectors have been widely used for many years. Teradyne Connection Systems of Nashua, N.H. sells blind mate optical connectors under the name HD Optyx™. These optical connectors are well suited for use with optical wave guides in the form of fiber that is physically separate from the daughter card and backplane board structures.
However, there is a desire to create optical interconnections within electronic systems by forming wave guides integrated within printed circuit boards. Such an architecture facilitates the use of electrical and optical signals within the same electronic system and increases the level of integration while reducing the number of optical fiber bundles running within a card cage enclosure. It has been proposed to embed optical fibers in the epoxy or other matrix material that provides structure to a printed circuit board. Other approaches for making optical wave guides as part of a printed circuit board assembly have also been explored. For example, optical wave guides might be formed by depositing transparent polymer in traces within the matrix.
While integrating the wave guide into the printed circuit board provides many advantages, there is currently a need for connectors that would allow optical signals to be routed from board to board. There is also a need for such connectors that would operate in a blind mate configuration.